It is known in the art to provide apparatus by which television images received at a local monitor may be given a three-dimensional appearance: one such arrangement is taught in Jurrison et al U.S. Pat. No. 4,286,286. In that system shuttering means are provided at the transmitter to alternately transmit signals representative of the appearance of a subject from two horizontally spaced viewpoints. The shuttering is correlated with the interlace components in the transmitted signal, and synchronized shuttering means are provided at the receiving monitor, to be worn as spectacles by the observer. The human brain functions, as is well known, to combine the rapidly alternating, slightly different right and left images to give the appearance of a three-dimensional image of the subject. The well known stereoscope of former decades is based on the same principal.